Solid propellant compositions



United States atent 3,9Z4,l43 Patented Mar. 6, 1952 fitice 3,024,143SSLHD PRGRELLANT CQMPOSHTIONS George D. Sammons and Richard C. Doss,Bartlesviile,

Qida, assignors to Phillips letroleurn Company, a corporation ofDelaware N Drawing. Filed May 16, 1958, Ser. No. 735,07 Claims. (Cl.149-19) This invention relates to solid propellant compositions. In oneaspect this invention relates to processing aids which can be used inthe manufacture of solid propellants. In another aspect this inventionrelates to additives which can be incorporated in a propellant mix tofacilitate the manufacture and/or ballistic properties of the finishedsolid propellant. In another aspect this invention relates toincorporating certain selected diamine dinitrates in solid propellants.

Solid propellants can be classified with respect to composition asdouble base type, single base type, and composite type. An example of adouble base propellant is ballistite which comprises essentiallynitroglycerine and nitrocellulose. Examples of single base propellantsare nitrocellulose and trinitrotoluene. Composite type propellants aregenerally composed of an oxidizer, and a binder or fuel. They maycontain other materials to facilitate manufacture or increase ballisticperformance such as a burning rate catalyst.

Rocket propellants have achieved considerable commercial importance aswell as military importance. Jet propulsion motors of the type in whichthe propellants of this invention are applicable can be employed to aida heavily loaded plane in take off. Said motors can also be employed asan auxiliary to the conventional power plant when an extra surge ofpower is required. Said motors can also be employed to propelprojectiles and land vehicles. Said propellants can also be used foruses other than propulsion. For example, they can be used as gasgenerators in starting devices, power units where a fluid is employed asa motive force, and other applications where a comparatively largevolume of gas is required in a relatively short period of time.

Recently, it has been discovered that superior solid propellantmaterials are obtained comprising a solid oxidant such as ammoniumnitrate or ammonium perchlorate, and a rubbery material such as acopolymer of butadiene and a vinylpyridine or other substitutedheterocyclic nitrogen base compound, which after incorporation is curedby a quaternization reaction or a vulcanization reaction. Solidpropellant mixtures of this nature and a process for their productionare disclosed and claimed in copending application Serial No. 284,447,filed April 25, 1952, by W. B. Reynolds and J. E. Pritchard.

Some solid propellant compositions are very difficult, if notimpossible, to mix by a dry mix method. Even if other mixing proceduresare successful, such as a solvent mixing technique, it is not alwayspossible to extrude the material. It has now been found that whencertain selected diamine dinitrates of the type described hereinafterare employed as additives in solid propellant compositions both themixing and extruding operations are greatly facilitated. In someinstances the propellant ingredients can be mixed by a dry mix methodand the resulting mix can be extruded if these additives are present,whereas such procedures cannot always be employed in the absence of theaddtives. An additional advantage is the increase in burning rate whendiamine dinitrates are present Thus, broadly speaking, the presentinvention resides in propellant compositions comprising an oxidantcompopent, a binder component, and a selected diamine dinitrate asdefined further hereinafter.

An object of this invention is to provide an improved propellantcomposition. Another object of this invention is to provide a processingaid for use in the manufacture of solid propellants. Still anotherobject of this invention is to provide a solid propellant having anadditive incorporated therein to facilitate the manufacture of, and/orimprove the ballistic properties of said propellant. Other aspects,objects, and advantages of the invention will be apparent to thoseskilled in the art in view of this disclosure.

Thus, according to the invention there is provided a propellantcomposition comprised of: a base propellant comprising an oxidantcomponent selected from the group consisting of ammonium nitrate andalkali metal nitrates, a binder component comprising a rubbery materialselected from the group consisting of natural rubber and syntheticrubbery polymers and mixtures thereof; and from 2 to 20 parts by weightper parts by weight of said base propellant of a diamine dinitratecharacterized by the structural formula wherein: R is an alkylene groupcontaining from 4 to 18 carbon atoms wherein at least 2 of said carbonatoms are in a chain between the nitrogen atoms; R is an alkyl groupcontaining from 1 to 4 carbon atoms, which alkyl groups can be alike andunlike; and wherein the total number of carbon atoms in the moleculedoes not exceed 24.

All diamine dinitrates and similar types of compounds are not operablein the practice of the invention. It has been found, for example, thatethylene diamine dinitrate, N,N,N,N'-tetramethyl1,Z-diaminoethanedinitrate, N,N, N,N-tetramethyl-1,2-diaminopropane dinitrate, and N,N,N',N'-tetramethyl-l,4-diaminobutene dinitrate show very little, if any,improvement in processing when employed in propellant composition of thetype herein described. Likewise, diethylenetriamine trinitrate givesvery little, if any, effect.

Representative diamine dinitrates which are operable in the practice ofthe invention include, among others, the following:

N,N,N,N'-tetramethyl-2,3-diaminobutane dinitrate;N,N,N,N-tetramethyl-3,4-diaminohexane dinitrate; N,N,N',N'tetramethyl-l,3-diamino-2-ethylpropane dinitrate;N,N,N',N'-tetramethyl-Z,4-diaminooctane dinitrate;N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate;N,N,N',N'-tetramethyl-1,4-diaminobutane dinitrate;N,N,N',N'-tetramethyl-2,S-diaminohexane dinitrate;N,N,N',N'-tetraethy1-l,S-diaminobutane dinitrate;N,N-dimethyl-N',N-diethyl-1,3-diaminobutane dinitrate;N,N,N,N-tetramethyl-1,5-diamino-octadecane dinitrate;N,N,N',N'-tetra-n-propyl-1,3-diaminobutane dinitrate;N,N,N',N'-tetran-butyl-1,8-diaminooctane dinitrate; N,N,N,N'tetramethyl-1,S-diamino-2,4-dimethylpentane dinitrate; N,N dimethyl N,Ndiethyl-1,8-diamino-3,6-dipentyloctane dinitrate; N,Ndimethyl-N',N-dipropyl-l,10-diamino-2,4,6,8-tetramethyldecane dinitrate;and N,N,N,N'-tetramethyl-1,8-diaminooctane dinitrate.

The amine nitrates employed in the practice of the invention can beprepared by several methods. One method is to react a suitable aminewith nitric acid. Another method which can be employed is to form a saltof the amine such as a hydrochloride or an acetate, and then react theamine salt with nitric acid.

The quantity of the diamine dinitrate employed is usually in the rangeof about 2 to about 20 parts by weight per 100 parts by weight of thebase propellant. As used herein and in the claims unless otherwisespecified, the term base propellant is defined as the binder componentplus the oxidant component.

The rubbery material employed in the binder component of the propellantcompositions of the invention can be a natural rubber, a syntheticrubbery polymer, or a mixture of natural rubber and said rubberypolymer. The term rubbery polymer as used herein and in the claims,unless otherwise specified is defined as including all rubbery polymersof olefins and diolefins which are prepared by either mass or emulsionpolymerization. Some examples of suitable rubbery polymers arepolybutadiene, polyisobutylene, polyisoprene, copolymers of isobutyleneand isopreue, copolymers of conjugated dienes with comonomers such asstyrene, and copolymers of conjugated dienes with polymerizableheterocyclic nitrogen bases. Said copolymers of conjugated dienes withpolymerizable heterocyclic bases comprise a pre* ferred class of rubberypolymers for use in the binder component of the propellants of theinvention. A presently preferred rubbery polymer is a copolymer of 1,3-butadiene with Z-methyl-S-vinylpyridine.

Said preferred class of rubbery polymers prepared by copolymcrizing aconjugated diene with a heterocyclic nitrogen base can vary inconsistency from very soft rubbers, i.e., materials which are soft atroom temperature but will how retraction when relaxed, to those having aMooney value (ML4) up to 100. The rubbery copolymers most frequentlypreferred have Mooney values in the range between 5 and 50. The may beprepared by any polymerization methods known to the art, e.g., mass oremulsion polymerization. One convenient method for preparing thesecopolymers is by emulsion polymerization at temperatures in the rangebetween 0 and 140 F. Recipes such as the ironpyrophosphate-hydroperoxide, either sugar-free or containing sugar, thesulfoxylate, and the persulfate recipes are among those which areapplicable. It is advantageous to polymerize to high conversion as theunreacted vinylpyridine monomer is difficult to remove by stripping.

The conjugated dienes employed are those containing from 4 to carbonatoms per molecule and include 1,3-butadiene, isoprene,2methyl-1,3-butadiene, and the like. Various alkoxy, such as methoxy andethoxy and cyano derivatives of these conjugated dienes, are alsoapplicable. Thus, other dienes, such as phenylbutadiene,2,3-dimethyl-1,3-hexadiene, 2-methoxy-3-ethylbutadiene,2-ethoxy-3-ethyl-1,3-hexadiene, Z-CyanQ-LS-butadiene, are alsoapplicable.

Instead of using a single conjugated diene, a mixture of conjugateddienes can be employed. Thus, a mixture of 1,3-butadiene and isoprenecan be employed as the conjugated diene portion of the monomer system.

The polymerizable heterocyclic nitrogen bases which are applicable forthe production of the polymeric materials are those of the pyridine,quinoline, and isoquinoline series which are copolymen'zable with aconjugated diene and contain one, and only one,

substituent wherein R is either hydrogen or a methyl group. That is, thesubstituent is either a vinyl or an alpha-methylviny=l (isopropenyl)group. Of these, the compounds of the pyridine series are of thegreatest interest commercially at present. Various substitutedderivatives are also applicable but the total number of carbon atoms inthe groups attached to the carbon atoms of the heterocyclic nucleusshould not be greater than because the polymerization rate decreasessomewhat with increasing size of the alkyl group. Compounds where thealkyl substituents are methyl and/or ethyl are available commercially.

4 These heterocyclic nitrogen bases have the formula where R is selectedfrom the group consisting of hydrogen, alkyl, vinyl, alpha-methylvinyl,alkoxy, halo, hydroxy, cyano, aryloxy, aryl, and combinations of thesegroups such as haloalkyl, alkylaryl, hydroxyaryl, and the like; one andonly one of said groups being selected from the group consisting ofvinyl and alpha-rnethylvinyl; and the total number of carbon atoms inthe nuclear substituted groups being not greater than 15. Examples ofsuch compounds are Z-Vinylpyridine;

2-vinyl-5 -ethylpyridine; Z-methyl-S-vinylpy-ridine; 4-vinylpyridine;

2,3 ,4-trimethyl-5 -vinylpyridine;

3 ,4,5 ,6-tetramethyl-2-vinylpyridine; 3-ethyl-5 -viny] pyridine;2,6-diethyl-4-vinylpyridine; 2-isopropyl-4-nonyl-5-vinylpyridine; 2methyl-5 -undecyl3 -vinylpyridine; 2,4-dirnethyl-5 ,6-dipentyl-3-viuylpyridine; 2-decyl-5-( alpha'methylvinyl) pyridine; 2-vinyl-3-methyl-5 -ethylpyridine; 2-methoxy-4-chloro-6-vinylpyridine;

3 -vinyl-5-ethoxypyridine;

2-vinyl-4,5-dichloropyridine;

2' alph a-methylvinyl) -4-hydroxy-6-cyanopyridine; 2-vinyl-4-phenoxy-5-methylpyridine;

2-cyano'5- alpha-methylvinyl) pyridine; 3-vinyl-5-phenylpyridine;

Z-(para-methyl-phenyl -3-vi-nyl-4-methylpyridine;

0 3-vinyl-5-(hydroxyphenyl) pyridine;

2-vinylquinolineg 2-vinyi-4-ethyl quinoline;3-vinyl-6,7-di-n-propylquinoline;

, 2-methyl-4-nonyl-6-vinylpyridine;

4 alph a-m ethylvinyl -8- do decyl quinoline;

3-vinylisoquinoline;

1,6-dimethyl-3-vinylisoquinoline;

2-vinyl-4-benzylquinoline;

3 -vinyl-5-chloroethylquinoline-3-vinyl-5 ,6-dichloroisoquinoline;

2-vinyl-6-ethoxy-7-methylquinoline;

3 -vinyl-6-hydroxymethylisoquinoline;

any of the well known methods employing well known recipes. Any of thewell known GR-S rubbers containing from 1 to 2 and up to about 25 partsof styrene can be used in the practice of the invention. The GR-S rubberdesignated as 1505 is one preferred copolymer for use in the practice ofthe invention. GR-S 1505 can be pretax,

pared by copolymerizing 1,3-butadiene with styrene at 41 F. using asugar free, iron activated, rosin-acid emulsified system. A chargeweight ratio of butadiene to styrene is 90/10 and the polymerization isallowed to go to approximately 52 percent completion. The copolymer isthen salt acid coagulated and usually has a mean raw Mooney value (ML-4)of about 40. Said copolymers usually have a bound styrene content ofabout 8 weight percent. Further details regarding the preparation ofGR-S rubbers can be found in Industrial and Engineering Chemistry, 40,pages 769-777 (1948), and United States Patents 2,583,277; 2,595,892;2,609,362; 2,614,100; 2,647,109; and 2,665,269.

The binder contains rubbery polymers of the type hereinbefore describedand, in addition, there can be present one or more reinforcing agents,plasticizers, wetting agents, and antioxidants. Other ingredients whichare employed for sulfur vulcanization include a vulcanizationaccelerator, a vulcanizing agent, such as sulfur, and an acceleratoractivator, such as zinc oxide. The finished binder usually containsvarious compounding ingredients. Thus, it will be understood that hereinand in the claims, unless otherwise specified, the term binder isemployed generically and includes various conventional compoundingingredients. The binder content of the propellant composition willusually range from 6 to 40 percent by weight.

A general formulation for the binder component of the propellantcomposition of the invention is as follows:

Parts by weight Rubber 100 Reinforcing agent 0-50 Plasticizer 0-100Wetting agent 0-10 Antioxidant 0-3 Vulcanization accelerator 0-5 Sulfur0-2 Metal oxide 0-5 Reinforcing agents which can be employed includecarbon black, wood flour, lignin, and various reinforcing resins such asstyrene-divinylbenzene, methyl acrylatedivinylbenzene, acrylicacid-styrene-divinylbenzene, and methyl acrylate-acrylicacid-divinylbenzene resins.

In general, any rubber plasticizer can be employed in the bindercompositions. Materials such as Pentaryl A (amylbiphenyl), Paraflux(saturated polymerized hydrocarbon), Circosol-ZXH (petroleum hydrocarbonsoftener having a specific gravity of 0.940 and a Saybolt Universalviscosity at 100 F. of about 2000 seconds), di(l,4,7- trioxaundecyl)methane, and dioctyl phthalate are suit able plasticizers. Materialswhich provide a rubber having good low temperature properties arepreferred. It is also frequently preferred that the plasticizers beoxygen-containing materials.

Wetting agents aid in deflocculating or dispersing the oxidizer. AerosolOT (dioctyl ester of sodium sulfosuccinic acid), lecithin, and Duomeen Cdiacetate (the diacetate of trimethylenediamine substituted by a coconutoil product) are among the materials which are applicable.

Antioxidants which can be employed include Flexamine (physical mixturecontaining 65 percent of a complex diarylamine-ketone reaction productand 35 percent of N,N'-diphenyl-p-phenylenediamine),phenyl-beta-naphthylamine, 2,2-methylenebis(4-methyl-6-tert-butylphenol), and the like. Rubber antioxidants, ingeneral, can be mployed or if desired can be omitted.

Examples of vulcanization accelerators are those of the carbamate type,such as N,N-dimethyl-S-tert-butylsulfenyl dithiocarbamate andButyl-Eight. Butyl-Eight is a rubber accelerator of the dithiocarbamatetype supplied by the R. F. Vanderbilt Company and described in Handbookof Material Trade Names by Zimmerman and Levine,

1953 edition, as a brown liquid; specific gravity 1.01; partiallysoluble in water and gasoline; and soluble in acetone, alcohol, benzol,carbon disulfide and chloroform.

It is to be understood that each of the various types of compoundingingredients can be used singly or mixtures of various ingredientsperforming a certain function can be employed. It is sometimespreferred, for example, to use mixtures of plasticizers rather than asingle material.

Oxidizers which are applicable in the solid propellant compositions ofthe invention are ammonium nitrate and the alkali" metal nitrates. Asused herein the term alkali metal nitrates includes sodium nitrate,potassium nitrate, lithium nitrate, caesium nitrate, and rubidiumnitrate. Ammonium nitrate is the presently preferred oxidizer. Mixturesof said oxidizers are also applicable. In the preparation of the solidrocket propellant compositions the oxidizers are ground to a particlesize preferably within the range between 20' and 200 microns averageparticle size. The most preferred particle size is from about 40 toabout 60 microns. The amount of oxidizer used is a major amount of thetotal composition and is usually within the range of about 60 to about94 weight percent of the base propellant, i.e., binder plus oxidizer.When ammonium nitrate is used as the oxidant component it is frequentlypreferred to use a phase stabilized ammonium nitrate. One method ofphase stabilizing ammonium nitrate comprises mixing about 10 parts byweight of-a potassium salt (usually potassium nitrate) with about partsby weight of ammonium nitrate along with some water, heating the mixtureto about F., drying, and then grinding the mixture to the desiredparticle size.

Burning rate catalysts applicable in the invention include ammoniumdichromate and metal ferrocyanides and ferricyanides. Ferricferrocyanides, such as Prussian, Berlin, Hamburg, Chinese, Paris, andmilori blue, soluble ferric ferrocyanide, such as soluble Berlin orPrussian blue which contains potassium ferric ferrocyanide, and ferricferrocyanide which has been treated with ammonia, are among thematerials which can be used. Ferrous ferricyanide, Turnbullss blue isalso applicable. A particularly effective burning rate catalyst ismilori blue, which is pigment similar to Prussian blue but having a redtint and is prepared by the oxidation of a paste of potassiumferrocyanide and ferrous sulfate. Other metal compounds such as nickeland copper ferrocyanides can also be employed. The amount of burningrate catalyst used, in the propellant compositions of this invention isusually in the range of 0 to 15 parts by weight per 100 parts by weightof the base propellant, i.e., oxidant plus binder.

The various ingredients in the propellant composition can be mixed on aroll mill or an internal mixer such as a Banbury or a Baker-Perkinsdispersion blade mixer can be employed. The binder forms a continuousphase in the propellant with the oxidant as the discontinuous phase. Oneprocedure for blending the propellant in gredients utilizes a stepwiseaddition of oxidant ingredient. The binder ingredients are mixed to forma binder mixture and the oxidizer ingredient, having the diaminedinitrate and burning rate catalyst (if one is used) dry blendedtherewith, is then added to said binder mixture in increments, usually 3to 5 but more can be used.

After the propellant composition has been formulated as indicated above,or by any other suitable mixing technique, rocket grains can be formedby extrusion.

The curing temperature will generally be in the range between 70 and 250F., preferably between and 200 F.

The curing time must be long enough to give required creep resistanceand other mechanical properties in the propellant. The time willgenerally range from around three hours, when the higher curingtemperatures are employed, to seven days when curing is effected atlower temperatures.

The following examples will serve to further illustrate the invention:

Example I A l,3-butadiene-2-methyl-S-vinylpyridine rubbery copolymer wasprepared by emulsion polymerization at 41 F. in accordance with thefollowing recipe:

Parts by weight 1,3 -butadiene 90 1 Fifty-five runs were made using theabove polymerization recipe. The latex was masterbatched with 19.5 partsof Philblack A (a trademark of Phillips Petroleum Company for a lowabrasion furnace carbon black) per 100 parts of rubber. The blackmasterbatch was then acid coagulated, washed with water, and dried. Theaverage conversion for these 55 runs was 85 percent in 17.0 hours. Theamount of modifier used in each run was in the range of 0.60 to 0.80part by weight.

Based on 100 parts by weight of rubber. v

Two and one-half parts by weight per 100 parts of rubber of saidlow-abrasion furnace carbon black was milled into the rubber prepared asdescribed above. This increased the amount of carbon black present to 22parts/100 parts of rubber.

The above-described composition was then placed in a 0.7 gallonBaker-Perkins mixer and 48 parts per 100 parts of rubber present ofliquid polybutadiene was added. Mixing was continued until a uniformbinder composition was obtained.

The liquid polybutadiene employed in said binder composition wasprepared by mass polymerization using finely divided sodium as thecatalyst. Said polybutadiene had the following properties:

Specific gravity, 60/60 F. 0.9059 Density at 60 F., lbs/gal. 7.5Refractive index, u 1.5174 Iodine number 365-385 Ash, wt. percent 0.05Color, Gardner 11 Volatile material, wt. percent 1.0 Saybolt Furolviscosity at 100 F 2500 Ingredients employed in two propellantcompositions prepared using the above-described binder were as follows:

Parts by weight Composition No Binder (as described above) 7 7 Ammoniumnitrate, commercial grade-- 92 88 Ammonium dichromate 1 1N,N,N,N-tetramethyl-l,3-diaminobutane dinitrate- 4 Total 100 100 wascontinued 10 minutes after consolidation of each increment and finally10 minutes under vacuum.

Said propellant compositions were extruded into strands approximately/2" in diameter employing various extrusion pressures. The followingextrusion data were obtained:

Extrusion Extrusion rate, pressure on inches/min. propellant,

p.s.i.

Composition N o. 1 (without N,N,N,N-tetramethyl-1,3-diarninobutanedinitrate additive) O. 12, 100 1. 25 14, 500 2 9, 080 Composition N o. 2(with said additive) 9 12, 100 16 14, 500

Composition No. 1 which did not contain theN,N,N,N-tetramethyl-1,3-diaminobutane dinitrate additive would notextrude at a pressure of 9,680 p.s.i. The data show that at saidpressure of 9,680 p.s.i., composition No. 2 containing said additiveextruded at the rate of two inches per minute. Composition No. 1 withoutsaid additive extruded at a slow rate of 0.75 inch per minute when thepressure was 12,100 p.s.i. while the extrusion rate was nine inches perminute at this pressure for composition No. 2 containing said additive.

Example 11 A /10 butadiene/Z-methyl-5-vinylpyridine rubbercarbon blackmaster-batch was prepared as described in Example I to give acomposition containing 22 parts of carbon black per parts of rubber.This composition was placed in a 0.7 gallon Baker-Perkins mixer and 30parts of di(3,6-dioxadecyl)formal, 5 parts of magnesium oxide, and 3parts of a physical mixture containing 65 percent of a complexdiarylamine-ketone reaction product and 35 percent ofN,N'-diphenyl-p-pheylenediamine, based on 100 parts of the rubber, wereadded. Mixing was continued until a uniform binder composition wasobtained.

The binder described above was employed for the preparation of twopropellant compositions as follows:

Mixing of the propellant compositions was the same as described forcomposition No. 2 in Example I. Said compositions were extruded intostrands approximately /2 in diameter. The extrusion pressure employedfor composition No. 3 was 14,500 p.s.i. For composition No. 4, whichcontained less dinitrate than composition No. 3, the extrusion pressurewas 16,950 p.s.i.

Past experience has shown that propellant compositions like compositions3 and 4 above, cannot be properly mixed by dry mixing techniques in theabsence of the diamino dinitrates of the invention. Such compositionscan be mixed (in the absence of said dinitrates) by employing a solventmixing technique which comprises dissolving the rubbery material of thebinder in a suitable solvent such as methylcyclohexane, incorporatingthe dry ingredients, and then removing the solvent by evaporation.However, the resulting mixtures cannot be extruded but Example III Abinder composition, prepared in the manner described in Example II,contained the following ingredients:

Parts by weight Butadiene/2-methyl-5-vinylpyridine copolymer 100PhilblackA 22 Di(3,6-dioxadecyl)formal 20 Flexamine 2 3 Magnesium oxide5 Total 150 1 As in Example I.

2 Physical mixture containing 65 percent of a complex diarylamineletonereaction product and 35 percent of N,N-diplienyl-p-phenyleneiamme.

The above-described binder was employed for the preparation of twopropellant compositions as follows:

Parts by weight Composition No 5 6 Binder 16. 5 16.5 Ammonium nitrate,commercial grade- 83. 5 83. 5 Ammonium dichromate 4 4 Milori blue 1 2 2N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate 4 Tom] 110. 0 106. 0

1 A burning rate catalyst widely used in propellants. It is a pigmentsimilar to Prussian blue but having a red tint and is prepared by theoxidation of a paste of potassium ferrocyamde and ferrous sulfate.

Extrusion pressure on propellant, p.s.1. Composition strand 346" strand3" grain Example IV A binder composition contained the followingingredients:

Parts by weight Butadiene/Z-methyl-5-vinylpyridine copolymer 1 100Philblack A 22 Di(3,6-dioxadecyl) formal 2O Magnesium oxide 5 Total 147I As in Example I.

The copolymer was put on a roll mill and the other binder ingredientswere added. Milling was continued until a homogeneous composition wasobtained. This 19 binder was employed in the following propellantformulations:

Parts by weight Composition No 7 8 Binder 16. 5 16. 5 Ammonium nitrate,commercial grade 83. 5 83. 5 Ammonium dichromate 4 4 Copper chromite 1 44 N,N,N,N-tetramethyl-1,3-diaminobutane dinitrate 4 10 Total 112. 0118.0

1 Harshaw Chemical Company commercial catalyst Cu0202.

Each composition was mixed as follows. The ammonium nitrate, ground to40 micron average particle size, was dry blended with the ammoniumdichromate and copper chromite and this blend was added in increments tothe binder on a roll mill. After all of said dry blend had been added,the mixture was cut off the mill, folded, and run through the millagain. The removing from the mill and folding process was repeated fivetimes after which the N,N,N',N'-tetramethyl-1,3- diaminobutane dinitratewas added. After being cut 01? and run through the mill three times(after the addition of the dinitrate) a composition wherein the dryblend ingredients were uniformly dispersed in the binder was obtained.

Strands 7 in diameter were extruded from each of the propellantcompositions 7 and 8 and from a control composition prepared in the samemanner but without incorporating any N,N,N',N'-tetramethyl-1,3-diaminobutane dinitrate. The strands were cured 24 hours at 180 F. and burningrate tests were made. Results were as follows:

Pressure exponent in r=aP where a is a constant, Fe is average chamberpressure, and r is burning rate.

Example V Two additional propellant compositions containing thefollowing ingredients were prepared:

Parts by weight Composition No 9 10 Binder 11 6 Ammonium nitrate 94 N,N,N 'N -tetramethyl-1,3-diaminobutane dinitrate..- 10

Total 111 The binder compositions were as follows:

Parts by Weight Masterbatch 1 8 6 MgO 1 Di(3,6-dioxadecyl)formal 2 Total111 6 1 The butadiene/Z-methyl-5-yinylpyridine copolymer. masterbatehedEvith carboin black (22 parts black/100 parts rubber), described inExample was use Composition No. 9 was mixed in the same manner asdescribed in Example I.

Composition No. 10 was prepared as follows. 30 parts by weight of thebinder component, cut into approximately A" cubes, was put into 317parts by weight of methylcyclohexane and the mixture stirred until thebinder was dissolved. The resulting solution was placed in a 0.7 gallonBaker-Perkins mixer and the ammonium nitrate was added. Mixing wascarried out for approximately minutes at room temperature to dispersethe ammonium nitrate in the binder solution. Vacuum was then appliedgradually, with continued mixing, until a final vacuum of about 70 mm.of mercury was reached. The temperature was then increased to about 140F., with continued mixing, and maintained at said temperature for about25 minutes to complete removal of the solvent. The resulting propellentcomposition was compression molded.

Burning rate test strands were extruded from composition No. 9 and werecut from composition No. 10. The following results were obtained inburning rate tests on said strands.

The above propellant compositions 9 and 10 show that increased burningrate due to the presence of the dinitrate additives of the invention isnot limited to those situations where a burning rate catalyst ispresent. While the propellant compositions 9 and 10 were not identical,it has been found that the presence of MgO and di(3,6- dioxadecyl)formalmakes little, if any, difference in the burning rate of a compositionsuch as the 11/90 and 6/94 base compositions of propellant compositions9 and 10.

The strand burning tests reported in the above examples were carried outby placing the strands, restricted on all surfaces except one end so asto prevent burning except on said one end, in a bomb and pressuring thebomb to the desired pressure with nitrogen. The bomb was then placed ina temperature bath maintained at 75 F. The strands were then ignited andthe time required for the propellant to burn between two fusible wiresspaced a known distance apart was recorded. The burning rate was thencalculated in inches per second.

As will be apparent to those skilled in the art various othermodifications of the invention can be made or followed in view of theabove disclosure without departing from the spirit and scope of saidinvention.

We claim:

1. A solid propellant composition comprising from 60 to 94 weightpercent of an oxidant component selected from the group consisting ofammonium nitrate and alkali metal nitrates, and from 6 to 40 Weightpercent of a binder component comprising a rubbery material selectedfrom the group consisting of natural rubber, synthetic rubber polymers,and mixtures thereof; and from 2 to parts by weight per 100 parts byweight of the total amount of said binder component plus said oxidantcomponent of a diamine dinitrate characterized by the structural formulawherein: R is an alkylene group containing from 4 to 18 carbon atomswherein at least 2 of said carbon atoms are in a chain between thenitrogen atoms; R is an alkyl group containing from 1 to 4 carbon atoms,which alkyl groups can be alike and unlike; and wherein the total numberof carbon atoms in the molecule does not exceed 24.

2. A propellant composition according to claim 1 wherein said oxidantcomponent is ammonium nitrate.

3. A propellant composition according to claim 1 wherein said rubberymaterial is natural rubber.

4. A propellant composition according to claim 1 wherein said rubberymaterial is a copolymer prepared by copolymerizing a conjugated dienecontaining from 4 to 10 carbon atoms with at least one RI CHZ=C/substituted heterocyclic nitrogen base selected from the groupconsisting of pyridine, quinoline, alkyl substituted pyridine and alkylsubstituted quinoline wherein the total number of carbon atoms in thenuclear alkyl substituents is not more than 15 and wherein R is selectedfrom the group consisting of a hydrogen atom and a methyl radical.

5. A propellant composition according to claim 4 wherein said copolymeris a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine.

6. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N,N-tetramethyl- 1,3-diaminobutane dinitrate.

7. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,-N,N'-tetramethyl- 3,4-diaminohexane dinitrate.

8. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N',N-tetramethyl- 1,3-diamino-2-ethylpropane dinitrate.

9. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N',N-tetramethyl- 2,3-diaminobutane dinitrate.

10. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N,N'-tetramethyl- 1,4-diaminobutane dinitrate.

11. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N,N-tetraethyl- 1,3-diaminobutane dinitrate.

12. A propellant composition according to claim 1 wherein said diaminedinitrate is N,N,N,N-tetra-n-propyl-1,3-diaminobutane dinitrate.

13. A propellant composition according to claim 1 wherein said rubberymaterial is a copolymer of 1,3- butadiene with styrene.

14. A propellant composition according to claim 1 wherein said oxidantcomponent is ammonium nitrate, said rubbery material is a copolymerprepared by copolymerizing a conjugated diene containing from 4 to 10carbon atoms with at least one substituted heterocyclic nitrogen baseselected from the group consisting of pyridine, quinoline, alkylsubstituted pyridine and alkyl substituted quinoline wherein the totalnumber of carbon atoms in the nuclear alkyl substituents is not morethan 15 and wherein R is selected from the group consisting of ahydrogen atom and a methyl radical and said amine dinitrate isN,N,N',N-tetramethyl- 1,3-diaminobutane dinitrate.

15. A propellant composition according to claim 14 wherein saidcopolymer is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridine.

16. A propellant composition according to claim 1 wherein said oxidantcomponent is ammonium nitrate and said rubbery material is a copolymerof 1,3-butadiene with 2-methyl-5-vinylpyridine.

17. A propellant composition according to claim 1 wherein said rubberymaterial is a copolymer of 1,3-butadiene with 2-methyl-5-vinylpyridineand said diamine dinitrate is N,N,NN-tetramethyl-1,B-diaminobutanedinitrate.

18. A propellant composition according to claim 2 13 wherein saidammonium nitrate is a phase stabilized ammonium nitrate.

19. A propellant composition according to claim 15 wherein said ammoniumnitrate is a phase stabilized ammonium nitrate.

20. A solid propellant composition comprising from 60 to 94 weightpercent of an oxidant component selected from the group consisting ofammonium nitrate and alkali metal nitrates, and from 6 to 40 weightpercent of a binder component comprising a rubbery material selectedfrom the group consisting of natural rubber, polybutadiene,polyisobutylene, polyisoprene, copolymers of isobutylene and isoprene,copolymers of conjugated dienes containing from 4 to carbon atoms permolecule with styrene, and copolymers of conjugated dienes contain from4 to 10 carbon atoms per molecule with at least one B! OHFC substitutedheterocyclic nitrogen base selected from the group consisting ofpyridine, quinoline, alkyl substituted pyridine and alkyl substitutedquinoline wherein the total number of carbon atoms in the nuclear alkylsubstituents is not more than and wherein R is selected from the groupconsisting of a hydrogen atom and a methyl radical; and from 2 to partsby weight per parts by weight of the total amount of said bindercomponent plus said oxidant component of a diamine dinitratecharacterized by the structural formula where: R is an alkylene groupcontaining from 4 to 18 carbon atoms wherein at least 2 of said carbonatoms are in a chain between the nitrogen atoms; R is an alkyl groupcontaining from 1 to 4 carbon atoms, which alkyl groups can be alike andunlike; and wherein the total number of carbon atoms in the moleculedoes not exceed 24.

OTHER REFERENCES Chem. and Eng. News, Oct. 7, 1957, pp. 623. ChemicalEngineering, April 21, 1958, pp. 126-9.

1. A SOLID PROPELLANT COMPOSITION COMPRISING FROM 60 TO 94 WEIGHTPERCENT OF AN OXIDANT COMPONENT SELECTED FROM THE GROUP CONSISTING OFAMMONIUM NITRATE AND ALKALI METAL NITRATES, AND FROM 6 TO 40 WEIGHTPERCENT OF A BINDER COMPONENT COMPRISING A RUBBERY MATERIAL SELECTEDFROM THE GROUP CONSISTING OF NATURAL RUBBER, SYNTHETIC RUBBER POLYMERS,AND MIXTURES THEREOF; AND FROM 2 TO 20 PARTS BY WEIGHT PER 100 PARTS BYWEIGHT OF THE TOTAL AMOUNT OF SAID BINDER COMPONENT PLUS SAID OXIDANTCOMPONENT OF A DIAMINE DINITRATE CHARACTERIZED BY THE STRUCTURAL FORMULA